For two weeks, anti-austerity protesters have been calling for the resignation of the government of President Omar Hassan al-Bashir, one of Africa's longest-serving leaders.

Sudan lost three-quarters of its oil output after South Sudan gained independence last year, forcing the government to impose cuts that have hit Sudanese who were already grappling with soaring inflation and a weakening currency.

On Sunday, police fired teargas and used batons to break up a protest of more than 250 people in the Ombada shantytown area, one of Khartoum's poorest neighborhoods, witnesses said.

The protesters chanted "No, no to rising prices", threw rocks at police and blocked a main street before security forces dispersed them, the witnesses said.

The police were not immediately available to comment, but have repeatedly denied using excessive force against protesters.

Earlier on Sunday, presidential assistant Nafie Ali Nafie was quoted as blaming the unrest on a conspiracy to provoke an "economic earthquake" in Sudan.

"Zionist institutions inside the United States and elsewhere ... are exploiting the latest economic decisions to destabilize the security and political situation," the state-linked Sudanese Media Centre quoted him as saying.

Nafie said the government had evidence of collusion between rebel groups in Darfur, politicians in arch-foe South Sudan and Zionist institutions in the United States to sabotage Sudan. He did not present the evidence.

The demonstrations have rarely gathered more than a few hundred people at a time, but have been an added pressure for Bashir's government, already trying to contain the economic crisis and multiple armed insurgencies.

Police used teargas to put down protests in several neighborhoods in Khartoum on Friday.

The Sudanese Commission for Defence of Freedoms and Rights estimated on Sunday that 1,000 people had been arrested since the protests began.

Demonstrators have chanted the widespread Arab Spring refrain: "The people want the downfall of the regime."

Unexpectedly, there was no official ceremony on Saturday to mark the 23rd anniversary of Bashir's bloodless coup.

Instead, Bashir attended the opening of a shopping mall in central Khartoum. Sudanese media reported the state would donate 20 percent of revenues from the mall to the poor.

Bashir is wanted by the International Criminal Court for war crimes in Darfur, charges Sudan has dismissed as baseless and politically motivated.